An inkjet printing apparatus for forming an image on a printing medium by applying ink onto the printing medium by use of a printing head has an advantage in that it can form small dots in high density with relatively less noise during printing and therefore used in various types of printings such as color printing. One type of such an inkjet printing apparatus has a printing head receiving an ink supply from an ink tank detachably connected thereto, a carriage having the printing head mounted thereon and moving the printing head relative to a printing medium in a scanning manner in a predetermined direction (main scanning direction), and a transfer mechanism transferring the printing medium relative to the printing head in a direction (sub scanning direction) perpendicular to the aforementioned predetermined direction, and performs printing by ejecting ink while the printing head scans in the main scanning direction. In this apparatus, printing heads ejecting color inks such as yellow, cyan, and magenta in addition to black are mounted on the carriage. By this configuration, not monochrome printing of a text image by using black ink but also full color printing by ejecting color inks can be made.
An ink supply system constituted of the ink tank and the printing head in such an inkjet printing apparatus has a mechanism where the ink tank and the printing head can be attached and removed to and from each other, and mostly, when the ink tank and the printing head are attached, an ink supply route from the ink tank to the printing head is simultaneously formed. This mechanism allows the ink supply route from the ink tank to the printing head to be shortened and thereby the size of the printing apparatus can be reduced. It is further advantageous in that the ink supply can be made by simply replacing the ink tank with a new one, thereby reducing running cost.
The above ink supply system, since the ink tank and the printing head are separable, is desired to satisfy at least the following conditions. First, leakage of ink must be prevented at the time when the printing head and the ink tank are attached and removed regardless posture of the ink tank. Second, ink is stably supplied while they are attached. Third, since it is presumable that a user may repeat attaching and removing of them, the conditions required during attaching and removing time must be satisfied in every single time such a attaching and removing are repeated.
Japanese Patent Application Laid-Open Nos. 07-241998 and 2000-289224 show an example of a conventional ink supply system. More specifically, a printing head has a conduit for introducing ink therein. When the printing head is attached to an ink tank, the conduit is brought into contact with an ink guide member within the ink tank. In this manner, ink from the ink tank is communicated to the printing head. By virtue of this mechanism of this system, ink can be supplied through a pipe-like member.
Japanese Patent Application Laid-Open Nos. 07-241998 and 2000-289224 further describe that an ink tank has an open/close valve serving as an ink supply route open/close mechanism. During removed time of the ink tank from the printing head, the ink tank is closed airtight by the valve, whereas, during attached time of the ink tank to the printing head, the valve is opened to form the ink supply route.
However, in the ink supply system having the ink supply route open/close mechanism described in Japanese Patent Application Laid-Open Nos. 07-241998 and 2000-289224, operations of attaching and removing the ink tank while opening and closing the valve respectively are operations including moving the ink tank in a vertical direction. Because of this, these operations cause a problem of spatial limitation for the printing apparatus, and a problem residing in that relatively complicated user's operation is required during attaching and removing of the ink tank. More specifically, in the ink supply system, the printing head is usually arranged below the ink tank and an open/close valve is attached to the bottom of the ink tank, as shown in Japanese Patent Application Laid-Open No. 2000-289224. This is because ink is allowed to gather at the bottom of the ink tank by gravitation and transfer efficiently to the printing head arranged below the ink tank so as not to leave ink in the ink tank. In this case, the ink supply route open/close mechanism opens the open/close valve, in most cases, by a vertical operation of the ink tank for attaching to the printing head. However, when the ink tank is installed by gaining access to the printing head downward from the right above, a relatively large space must be kept above the region where the printing head moves in a scanning manner, for the user's operation for installation. More specifically, it is necessary to keep the space corresponding to the length of the ink tank in the insertion direction or the space large enough for the user's hand having the ink tank to get in. Such a large space gives limitations when a printing apparatus is designed. Furthermore, in a so-called front loading type printing apparatus often employed in facsimiles (multifunction printers), it is difficult to apply the aforementioned system where attaching/removing of an ink tank placed in the above is performed.
Furthermore, when the ink tank is installed to the printing head by approaching the ink tank to the printing head vertically from above, the ink tank must be installed to the printing head while aligning the open/close valve of the ink tank with a connecting portion of the printing head. Therefore, the operation for installation becomes complicated. In connection with this, it is a trend to be desired that a printing apparatus is made compact with a reduced height. Therefore, the number of ink tanks low in height when installed to a printing heads has been increased. Accordingly, the length of the ink tank in the horizontal direction has been increased by just that much in order to keep the volume of the ink tank without reducing Therefore, when such a horizontal-long ink tank is installed, if the ink tank is tilted even slightly during the installation, positional deviation takes place between the open/close valve and the connecting portion of the printing head. Because of the positional deviation, it is necessary for the user to perform a relatively intricate operation for aligning them. If the ink tank is forcibly installed while the open/close valve and the connecting portion are aligned with deviation, leakage of ink may occur and the open/close valve may be broken.
To align between the open/close valve and the connecting portion of the printing head, it may be conceivable that a guide is provided to the printing head and the ink tank to improve the alignment accuracy during the installation. However, the presence of the guides complicates the structure of the apparatus.